[en] An efficient method for obtaining solutions of three-dimensional LWR core transients with void feedback was developed. A modified version of the so called adiabatic approach is used to solve the transient neutronic calculations. The effective multiplication factor obtained from the shape equation is used in the amplitude equation to predict the power level for the next time step. The partial convergence approach, which incorporates the thermal hydraulic and neutronic calculations in a single package and converges on both solutions simultaneously, is adapted to the transient computations. Due to flow channel geometry differences, the thermal hydraulic calculations are treated differently for PWR's and BWR's. A zero radial pressure gradient is assumed in order to solve for the flow redistribution among the open channels in a PWR. The quasi-static momentum integration method, along with the assumption a uniform pressure drop through the flow channels, is used to determine the inlet flow distribution in a BWR. This approach is believed to be a considerable improvement over methods previously available; it presents the simplicity of the adiabatic formulation while leading to an accuracy comparable to that of the usual quasi-static approach